ASME B36.19 Pipe Dimension, Wall Thickness and Weight

ASME B36.19 is the standard that defines the dimensions of stainless steel pipe - its outside diameter, the wall thickness for each 'S' schedule (5S, 10S, 40S, 80S, 160S), and its weight. A B36.19 pipe schedule chart turns a nominal pipe size and an 'S' schedule into the actual wall thickness and weight of the pipe.

On this page you will find the complete ASME B36.19 stainless steel pipe dimension and weight charts for NPS 1/8 through NPS 30, plus a plain-language guide to reading the 'S' schedule codes, choosing the right wall thickness, and understanding how schedule relates to pressure. All dimensions are shown in both inches and millimetres. For carbon and alloy steel equivalents, see the ASME B36.10 steel pipe schedule charts.

Quick answer: TL;DR: The 'S' in 5S, 10S, 40S, 80S means 'stainless' - these walls are thinner than the matching carbon-steel schedule because stainless is stronger. Schedule is a wall-thickness code, not a measurement; 40S equals Standard Weight and 80S equals Extra Strong for most sizes.

Quick Reference - ASME B36.19 at a glance

Item	Value / Note
Standard	ASME B36.19M - Welded and Seamless Wrought Stainless Steel Pipe
Material family	Stainless steel (austenitic, ferritic, duplex, and similar alloys)
Size range (charts here)	NPS 1/8 through NPS 30 (DN 6 to DN 750)
Schedules	5S, 10S, 40S, 80S, 160S (the 'S' stainless series)
Defines	Outside diameter (OD), wall thickness by schedule, and plain-end weight
OD rule	Same outside diameter as ASME B36.10 for the same NPS
40S / 80S	Equal to STD / XS for most sizes; 5S and 10S are thinner than any B36.10 light wall
Pressure rating?	B36.19 gives dimensions only; pressure comes from ASME B31.3 with material and temperature

What Is ASME B36.19 and What Does It Cover?

ASME B36.19 defines the dimensions of stainless steel pipe - outside diameter, wall thickness for each 'S' schedule, and weight - but it does not set pressure ratings or material grades. Those come from separate piping and material standards.

The standard, titled Welded and Seamless Wrought Stainless Steel Pipe, covers stainless pipe in sizes from NPS 1/8 (Nominal Pipe Size) through NPS 30 in the dimensional tables presented here. It applies to both welded and seamless stainless pipe. Like B36.10 for carbon steel, it establishes a consistent set of outside diameters and a schedule system so that fittings, flanges, and valves from different makers can interconnect.

What B36.19 is not matters just as much. It is a dimensional standard, not a pressure standard and not a material standard. The allowable pressure of a given pipe is calculated under a piping code such as ASME B31.3 using the stainless grade's allowable stress at temperature. The material grade itself is specified by ASTM product standards such as A312 (austenitic), A790 (duplex), or A358 (welded austenitic), which we cover later in this guide.

What Does "Pipe Schedule" Mean, and What Does the "S" Stand For?

Pipe schedule is a dimensionless index that groups wall thicknesses. In ASME B36.19 the schedules carry an 'S' - 5S, 10S, 40S, 80S, 160S - which marks them as the stainless-steel series with walls that are equal to or thinner than the matching carbon-steel schedule.

Schedules were introduced in the 1930s-40s to standardise wall thickness as mills moved from the old 'standard weight', 'extra strong', and 'double extra strong' names toward a numbered system. ASME B36.19 uses the stainless 'S' series: 5S and 10S are thin-wall pipes; 40S is the stainless equivalent of Standard Weight (STD); 80S is the stainless equivalent of Extra Strong (XS); and 160S is a heavy-wall stainless option available in the smaller sizes.

A frequent point of confusion is that the schedule number is not a thickness in inches or millimetres, and the same schedule does not give the same wall across different sizes. For a 1 inch pipe, Schedule 40S wall is 0.109 in (2.77 mm); for a 12 inch pipe, Schedule 40S wall is 0.375 in (9.52 mm). The 'S' tells you it is the stainless series; the chart tells you the actual wall.

How Do You Read the Wall Thickness Code on a Pipe?

To read a pipe's wall thickness, decode the stamped marking for its nominal size and schedule, then look up that NPS + 'S' schedule pair in the ASME B36.19 chart to read the wall thickness (in and mm) and the weight. The schedule on the pipe is the code; the chart converts it to an actual dimension.

A typical stainless pipe marking reads something like: NPS 6 SCH 40S ASTM A312 TP316L. Breaking that down:

1. NPS 6 - the nominal pipe size (approximately 6 inches). Look in the NPS column of the chart.

2. SCH 40S - the schedule code with the 'S' stainless series. Find the Schedule 40S column under that NPS.

3. Read the wall - at NPS 6, Schedule 40S the chart gives a wall of 0.280 in (7.11 mm) and a weight of 18.99 lb/ft (28.26 kg/m).

4. Confirm by measuring - on an existing pipe, measure the outside diameter with a tape and the wall with an ultrasonic gauge; then match both to the chart to confirm the schedule.

Two rules make the code readable. First, NPS is not the outside diameter. For NPS 1/8 through 12, the OD is larger than the nominal number (NPS 1 = 1.315 in OD; NPS 12 = 12.750 in OD). For NPS 14 and larger, the OD equals the nominal number exactly (NPS 14 = 14.000 in OD). Second, the international 'DN' (Diamètre Nominal) is simply NPS x 25.4 mm, so NPS 6 is about DN150. The 'S' suffix is the final clue: it marks the row as the stainless-steel wall series. With these rules and the charts below, any wall-thickness code becomes a concrete dimension.

ASME B36.19 Stainless Steel Pipe Dimension and Weight Charts

The tables below present the complete dimensional specifications for ASME B36.19 stainless steel pipe by schedule. For every nominal size the outside diameter is constant and only the wall thickness - and therefore the weight - changes with schedule.

All dimensions are presented in both metric (millimetres, kg/m) and imperial (inches, lb/ft) units. Use the charts to confirm wall thickness, outside diameter, and weight for any NPS and 'S' schedule combination. Note that Schedule 160S is listed only through NPS 6, and the largest sizes (NPS 24-30) are available in 5S, 10S, 40S, and 80S.

Need only the most common sizes? See the Sch 40 steel pipe dimensions and weight and Schedule 80 steel pipe dimensions and weight guides for focused charts, and the stainless steel pipe schedule chart for a compact summary.

Standard Schedules in ASME B36.19 Explained

The B36.19 'S' schedules run from thin-wall 5S and 10S up to heavy-wall 160S; 40S (Standard Weight) and 80S (Extra Strong) are the workhorses of stainless process piping.

Each schedule is a band of wall thickness. As a rule of thumb, the higher the number, the thicker and heavier the pipe and the higher its pressure capability for a given stainless grade:

How Does Schedule Relate to Pressure Rating?

Schedule controls wall thickness, and wall thickness controls pressure capacity - but the actual allowable pressure also depends on the stainless grade and the service temperature, not on the schedule alone.

The piping code formula (simplified, ASME B31.3) is: P = 2 * S * E * t / (D - 2*y*t), where P is allowable pressure, S is the material's allowable stress at temperature, E is the quality factor (1.0 for seamless), t is the wall thickness, and D is the outside diameter. Because S varies by grade, two pipes of the same NPS and 'S' schedule - say 304L versus 316L, or 316 versus a duplex 2205 - will carry different pressures. Schedule 40S and 80S are the standard reference points, but the rating is always a material-and-temperature calculation, never a property of the schedule number by itself.

One practical advantage of stainless: its allowable stress is higher than carbon steel's, so a given 'S' schedule of stainless pipe can often carry more pressure than the same carbon-steel schedule. That is exactly why B36.19 can use thinner walls than B36.10 for comparable service. For the deeper pressure side, see the Schedule 80 pressure rating and properties article.

ASME B36.19 vs ASME B36.10 - Which Standard Applies?

Use ASME B36.19 for stainless steel pipe, and ASME B36.10 for carbon and alloy steel pipe. The two standards share the same NPS/OD logic but use different schedule series and wall thicknesses.

B36.19 stainless pipe uses the 'S' schedule series (5S, 10S, 40S, 80S, 160S) with thinner walls than the equivalent B36.10 schedule, because stainless is stronger and corrosion allowance is handled differently. For the same NPS, 40S matches Standard Weight and 80S matches Extra Strong, but B36.19 does not carry the full carbon-steel range (it omits 10, 20, 30, 60, 100, 120, 140 and XXS). The chart below summarises the split.

Materials and Grades Used with B36.19 Pipe

ASME B36.19 sets the shape; the stainless grade is set by a separate ASTM product standard. Austenitic 300-series grades dominate, with duplex grades used for aggressive chloride service.

JN Alloy supplies the full range - from stainless steel pipe and duplex steel pipe to Hastelloy and nickel-alloy pipe - all cut and processed to ASME B36.19 dimensions. Pair the pipe with the right butt-weld fittings and flanges for a complete, standards-matched system.

How to Choose the Right Schedule for Stainless Pipe

Choose the 'S' schedule from the required pressure and temperature, the needed corrosion allowance, and any mechanical loads. When nothing special applies, 40S is the safe default; move to 80S - or 160S in small sizes - when pressure, abrasion, or corrosion margin demands more wall.

• Pressure / temperature: calculate the required wall with the ASME B31.3 formula using your grade's allowable stress; pick the next standard 'S' schedule up.

• Corrosion allowance: if the fluid will thin the wall over time, start with a heavier schedule (e.g., 80S instead of 40S) so the pipe still meets minimum wall at end of life.

• Mechanical load: for spans, supports, and external loads, the heavier wall of 80S or 160S adds stiffness.

• Weight and cost: heavier schedules cost more and weigh more; over-specifying wastes money and complicates support design.

If you are deciding between the two most common options, the difference between Schedule 40 and Schedule 80 stainless steel pipe article breaks down the trade-offs. For a focused stainless summary, see the stainless steel pipe dimensions and chart page.

Frequently Asked Questions